1. Field of the Disclosure
The present invention relates generally to controlling a power converter. More specifically, examples of the present invention are related to controlling switch mode power converters.
2. Background
Switch mode power converters are widely used for household or industrial appliances that require a regulated direct current (dc) source for their operation, such as for example battery chargers that are commonly used in electronic mobile devices. Off-line ac-dc converters convert a low frequency (e.g., 50 Hz or 60 Hz) high voltage ac (alternating current) input voltage to a required level of dc output voltage. Various types of switch mode power converters are popular because of their well regulated output, high efficiency, and small size along with their safety and protection features. Popular topologies of switch mode power converters include flyback, forward, boost, buck, half bridge and full bridge, among many others including resonant types.
Some switch mode power converters, such as a synchronous switch mode power converter, may include a first switch on the primary side of the power converter and also a second switch, such as a switch of a synchronous rectification circuit, on the secondary side of the power converter. The first switch may be switched between an ON state (i.e., closed switch) and an OFF state (i.e., open switch) to control the energy transfer between the input and the output of the power converter. The second switch may be used to increase the efficiency with which the energy is transferred to the output of the power converter when the first switch is switched to the OFF state. In operation, the second switch may be switched between the ON state and the OFF state in coordination with the first switch such that both switches are not in ON state simultaneously to prevent a condition where the power converter attempts to provide energy to a short circuit at the output that may lead to a reduction in the efficiency of the power converter.
A synchronous switch mode power converter may operate in both a continuous conduction mode and a discontinuous conduction mode depending on a load condition at the output of the power converter. It may be desirable for the power converter to run efficiently in both operation modes. Therefore, the secondary side of the power converter may coordinate the control of the second switch with the primary side of the power converter to ensure that the first switch and the second switch are not in ON state at the same time in both the continuous conduction mode and the discontinuous conduction mode.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.